1. Field of the Invention
The present invention relates to circuitry for and a method of diagnosing electrical failures of remotely driven inductive loads, and failures of electrical connections between a master module and a remotely located power module.
2. Description of Related Art
Many conventional electronic controllers require a signal (or signals) to diagnose the status of output lines. When a controller drives inductive loads, a typical diagnostic procedure may call for checking that a fly-back voltage pulse is generated when each inductive load is switched. Conventionally, dedicated wires and pins are needed to convey such diagnostic information in the form of the fly-back voltage pulse. Recently, design constraints in automotive design require that the number of input and output pins and wires be kept to a minimum so as to lower the cost of the electronic control system, but without sacrificing reliability. Under such constraints, dedicated wires and pins are no longer a viable design option.
In automotive or industrial systems it is sometimes essential to place the power device drivers close to the loads but separate from the controller (microcomputer, etc.). The reasons to do this can be for safety, cost, noise and etc. However, the diagnostic problem becomes more complex when the loads are remotely driven (i.e., where the power drivers are physically separated from the controller). For example, the length of diagnostic lines would be great.
It would therefore be desirable to provide circuitry for and a method of ascertaining the diagnostics of inductive loads without relying on dedicated input and output pins and wires.
One aspect of the invention relates to mixing diagnostic information, such as a fly-back pulse or pulses that correspond to specific waveform characteristics of one sequentially driven inductive load, onto a presently unused control signal line from which another one of the loads will be driven. After mixing, the diagnostic information is transmitted from a remote module to a physically separate master module via at least one connection line between the modules that carries a control signal other than that which drove the inductive load, thus yielding the diagnostic information back at the master module.
In an illustrative embodiment of the invention, an apparatus and method for detecting diagnostic information of sequentially driven loads is realized by:
sequentially driving inductive loads in response to the transmission of associated control signals from a master module to a remote module via respective connection lines, the modules being physically separate from each other and the connection lines electrically connecting the modules together;
generating diagnostic signals in sequence that correspond with specific waveform characteristics of the output current from respective driven inductive loads; and
multiplexing the diagnostic signals in sequence into a pulse train and transmitting pulses of the pulse train to the master module via sequential ones of the connection lines so that the diagnostic signals associated with each currently driven one of the inductive loads are transmitted through a next one of the connection lines that is other than that through which the currently driven one of the inductive loads was sequentially driven.